JP2876450B2 - Pneumatic radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having at least a groove extending in a circumferential direction in a tread and suitable for running on a snowy road surface.

[0002]

2. Description of the Related Art An annular tread, a pair of sidewalls extending inward in the tire radial direction from both ends of the tread,
In a pneumatic radial tire having an annular bead provided at an inner end of a sidewall, a tread surface is generally provided with a tread pattern including a circumferential groove, a lug groove extending in a tread width direction, a siping, and the like. ,
It has improved drainage performance, ensured steering stability on wet roads, and ensured running performance on muddy roads and snowy roads. For example, the conventional tread pattern shown in FIG. 2 has two central main grooves a extending circumferentially at a predetermined distance in a tread central portion, and two central grooves extending circumferentially outward of the central main groove a in the tread width direction. Sub-groove b, two circumferentially extending sub-grooves c provided in shoulder portions at both ends of the tread, and a lug groove d extending in the tread width direction having both ends opened to the central main groove a and the sub-main groove b. A lug groove e extending in the tread width direction with both ends opened to the sub main groove b and the sub groove c; and a block f formed by the central main groove a, the sub main groove b, the sub groove c, and the lug groove e. Is provided.

[0003]

However, the conventional tread pattern has a problem in that the number of sipes per block is small and the rigidity of the block f is high, so that the performance on snow is insufficient. Therefore,
In order to improve the performance on snow by reducing the rigidity of the block f, if the number of sipings per block is increased over the entire tread, the rigidity of the block f is excessively reduced,
There is a problem in that the running performance and wear resistance on a muddy road surface and the steering stability on a dry road surface are reduced. Also,
Increase the number of sipes per block in one part of the tread (eg, in the center), and in other parts (eg,
The number of sipes per block in the shoulder part) is reduced, the rigidity of some (central part) blocks is reduced to improve the performance on snow, and the other parts (shoulder part)
By keeping the high, it is conceivable to secure the running performance and wear resistance on muddy roads and the steering stability on dry roads, but some (center) blocks and other parts Since the rigidity of the (shoulder) blocks is different, there is a problem that the riding comfort performance is reduced.

[0004] It is an object of the present invention to provide a pneumatic radial tire having improved riding comfort, steering stability on wet roads, and on-snow performance without deteriorating steering stability on dry roads.

[0005]

To achieve the above object, a pneumatic radial tire according to the present invention comprises an annular tread, a pair of sidewalls continuous with both ends of the tread,
A pneumatic radial tire having a bead at the inner end of a sidewall, wherein at least two
A main groove extending substantially linearly in the circumferential direction of the book, a center land portion extending circumferentially in the tread equator formed between the two main grooves extending across the tread equator, and a center land portion other than the center land portion Is provided only in the land portion, one end is opened in the main groove, the other end is opened in another main groove or the tread end portion, and the groove width for dividing the land portion into a plurality of blocks is 1.5 mm or more and less than 5 mm. A lug groove is provided on the center land portion, and both ends are opened in the main grooves on both sides to divide the center land portion into a plurality of center blocks, and at the same time exceeding 20 degrees with respect to the tread equatorial plane.
Has an angle of less than 0 degrees
Are alternately arranged and the center block has a substantially triangular shape
The main siping is defined in the center block, the auxiliary siping is provided in the center block, one end is open in one of the main grooves on both sides, and the other end is terminated in the center block. Provided in the block, one end is open to the main groove, the other end is open to the main groove, lug groove or tread end and splits each side block into two small blocks, and each small block An auxiliary siping is provided, one end of which is open to the main groove or the lug groove, and the other end of which is terminated in the small block. According to this configuration, the land part is divided by the lug groove, so the rigidity of the land part is reduced and the running performance on snow is improved, while the drainage performance is improved by the lug groove and the steering stability on wet road surface is secured I do. In addition, the center land is divided into a plurality of center blocks by main siping to reduce rigidity, improve running performance on snow, and improve riding comfort. Further, by providing the auxiliary siping, the rigidity between the center block and the other blocks is made uniform, and the riding comfort is improved. In addition, by dividing each block into small blocks by the main siping provided on land parts other than the center land part, the rigidity of the blocks is reduced, so that running performance on snow is improved and riding comfort is improved. By providing the auxiliary siping, it is possible to further reduce the rigidity of each block, further improve running performance on snow, and improve riding comfort. It should be noted that four circumferentially extending main grooves provided on the tread, and a main land portion between the equatorial side main groove and the shoulder side main groove are provided on a block forming both ends of the main groove. The main siping that divides the central land block into two small blocks by opening into the main land, and a shoulder land part between the main groove on the shoulder side and the end of the tread is provided at one end of the shoulder side. And a main siping opening the other end to the lug groove or tread end and dividing the shoulder land block into two small blocks.

[0006]

An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, a tread T has two center main grooves 1 provided on the center side in the width direction and extending in the tire circumferential direction.
(1A, 1B), a center land portion 2 formed between the two center main grooves 1, and two middles extending in the tire circumferential direction and provided on the tread end TO side of the center main groove 1. The main grooves 3, 3; a central land portion 4 formed between the center main groove 1 and the middle main groove 3; and a shoulder land portion 5 formed between the middle main groove 3 and the tread end TO. Have.

The central land portion 4 is divided into a plurality of central blocks 41 by lug grooves 6 provided at both ends with openings in the center main groove 1 and the middle main groove 3. The shoulder land portion 5 has one end opened in the middle main groove 3 and the other end divided into a plurality of shoulder blocks 51 by a lug groove 7 reaching at least the tread end TO. Lug grooves 6, 7
Has a groove width of 1.5 mm or more and less than 5 mm and a groove depth of 50% or more of the groove depth of the center main groove 1 and the middle main groove 3.

According to this configuration, the central land portion 4 and the shoulder land portion 5 are divided into the central block 41 and the shoulder block 51 by the lug grooves 6, 7, respectively, and the rigidity of the central land portion 4 and the shoulder land portion 5 is reduced. As a result, the running performance on snow is improved, and the drainage performance is improved by the lug grooves 6 and 7, and the steering stability on wet road surfaces is secured. When the lug grooves 6, 7 are not open in the center main groove 1 or the middle main groove 3, or when the lug grooves 6, 7 have a groove width of less than 1.5 mm, the rigidity of the center block 41 and the shoulder block 51 is high. As a result, the running performance on snow decreases, the drainage performance decreases, the steering stability on wet road surfaces decreases, and the riding comfort performance also decreases. When the width of the lug grooves 6 and 7 is 5 mm or more, the rigidity of each block becomes too high, the steering stability on a dry road surface is reduced, and the wear resistance is reduced.

The center land portion 2 is provided on the center block 21 and a main siping 8 having both ends opened to the center main grooves 1A and 1B on both sides to divide the center land portion 2 into a plurality of center blocks 21. One center main groove 1A
And an auxiliary siping 81A whose other end extends to the equator side of the tread T and terminates in the center block 21, and one end opens to the other center main groove 1B and the other end extends to the equatorial side of the tread T. An auxiliary siping 81B extending and terminating in the center block 21 is provided. In addition, the main siping 8 is provided at an angle of more than 20 degrees and less than 70 degrees with respect to the equatorial plane of the tread, and the inclination directions of two adjacent sipes 8A and 8B are different. 8A and the sipe 8B rising to the left are alternately arranged, and the widened portions 10A and 10B are provided in the center main grooves 1A and 1B, respectively.
One end of each of the sipes 8A and 8B is open, and the center block 21 is formed in a substantially triangular shape. In addition, the auxiliary siping 81 (81A, 81B)
Main siping 8 with an angle of more than 20 degrees and less than 70 degrees
Is provided in the middle of the opening position to the main groove 1.

According to this configuration, the main siping 8 divides the center land portion 2 into a plurality of center blocks 21 to reduce rigidity, improve running performance on snow, and improve riding comfort. Center block when the inclination angle of the main siping 8 with respect to the tire width direction is 20 degrees or less
The lateral stiffness of the 21 will be excessively reduced, and the steering stability on dry roads will be reduced.If it is more than 70 degrees, the lateral stiffness of the center block 21 will be excessively increased, and the running performance on snow Decrease. In addition, auxiliary siping 81A, 81B
By providing, the center block 21 and other parts,
That is, the central block 41 of the central land portion 4 and the shoulder land portion 5
Of the rigidity between the shoulder block 51 and
Improve ride comfort.

In the central land portion 4, one end is opened in the center main groove 1 and the other end is opened in the middle main groove 3 or lug groove 6, and each central block 41 is divided into two central small blocks 42, 42. And the auxiliary siping 91 provided in each central small block 42 and having one end opened in the center main groove 1 or the middle main groove 3 and the other end terminated in the central small block 42. Is provided. The main siping 9 of the central block 41 may have one end opened in the middle main groove 3 and the other end opened in the center main groove 1 or the lug groove 6. The auxiliary siping 91 is formed in the lug groove 6. It may be open. In the shoulder land portion 5, one end is opened in the middle main groove 3 and the other end is opened in the lug groove 7 to divide the shoulder block 51 into the shoulder small blocks 52, and each shoulder small block 52 An auxiliary siping 101 is provided, one end of which is open in the middle main groove 3, and the other end of which is terminated in the shoulder small block 52.

According to this construction, the central block 41 and the shoulder block 51 are divided into the central small block 42 and the shoulder small block by the main grooves 1 and 3 or the main sipes 9 and 10 opened to the main groove 1 or 3 and the lug groove 6. Since the rigidity of the center block 41 and the shoulder block 51 is reduced by being divided into the blocks 52, the running performance on snow can be improved and the riding comfort can be improved. If one end of the main sipes 9 and 10 is not open in the main grooves 1 and 3 or the lug grooves 6, the rigidity of the central block 41 and the shoulder block 51 is high, the running performance on snow is deteriorated, and the riding comfort is reduced. become worse. Further, by providing the auxiliary sipes 91 and 101, the center block 41 and the shoulder block 51 are provided.
The rigidity of the tires can be further reduced to further improve the running performance on snow and improve the riding comfort. By providing the auxiliary sipes 91 and 101, the running performance on snow and the riding comfort can be improved by the tread pattern. The size of the material is large, the range of choice of the material of the tread rubber is widened, and deterioration of other performances is reduced. When both ends of the auxiliary sipes 91 and 101 are opened in the main groove or the like, the rigidity of the center block 41 and the shoulder block 51 is excessively reduced, and the running performance on a dry road surface is reduced. Further, each shoulder block 52 is provided with an auxiliary siping 102 having one end open to the tread end and the other end terminating in the shoulder block 52. Auxiliary siping 102
By providing, the rigidity of the shoulder block 52 can be reduced, the running performance on snow can be further improved, and the riding comfort can be improved.

Next, an example tire to which the present invention is applied,
An experimental result using a comparative example tire having another structure will be described. The tire size is 225 / 60ZR16, and it is assembled on a rim of size 7J × 16, and the internal pressure is 2.0 kg / cm ²
A running test was conducted by mounting it on a domestic FR car (4,000 cc), and the results are shown in Tables 1 and 2. Example tire: A tire provided with a tread pattern having the structure shown in FIG. Comparative Example Tire I: A tire in which the main sipe at the center land portion was halved (only the main sipe inclined in one direction was used) compared to the example tire. Comparative tire II: A tire in which the auxiliary sipe in the central land portion is extended and both ends are opened in the main groove, as compared with the example tire. Driving stability and ride comfort tests are sensory evaluations by drivers. The braking test is an average of three times, excluding the maximum and minimum, with the brakes that lock all four wheels at the speed of 60 km / h and the braking distance is measured five times. In the wear resistance test, the occurrence of uneven wear was checked after running 20,000 km on a general road (expressway / general road = 70/30). Note that the index display is based on the comparative tire I (10
0) indicates that the larger the numerical value, the better the performance.

[Table 1] Driving Stability Driving Stability Riding Comfort Uneven Wear Resistance (Dry) (Wet) Comparative Example Tire 100 100 Hard (100) Good Good Example Tire 95 105 Good (110) Good Good Comparative Example Tire II 90 105 Good (115) Wear occurred in the central land part Note) Wear generated in the comparative example tire II is heel and toe wear with a maximum depth of 1.5 mm generated in the central land part. The steering stability of the example tire on a wet road surface is improved in stickiness. [Table 2] Test on snow compaction Test on ice floe Driving stability Braking test Driving stability braking test Comparative tire I 100 100 100 100 Example tire 100 101 105 102 Comparative tire II 105 102 110 104

From the results shown in Tables 1 and 2, when the main siping in the center land area is reduced, the steering stability and riding comfort on wet road surfaces are deteriorated, and the steering stability on ice sheets is also deteriorated. Further, if the auxiliary siping in the central land portion is extended to open both ends into the main groove, the rigidity of the block is excessively reduced, so that the steering stability on a dry road surface is deteriorated, and the uneven wear resistance is reduced.

[0016]

Since the present invention is configured as described above, the following effects can be obtained. Since the land portion is divided by the lug groove, the rigidity of the land portion is reduced and the running performance on snow is improved, and the drainage performance is improved by the lug groove, and the steering stability on the wet road surface is secured. In addition, the center land is divided into a plurality of center blocks by main siping to reduce rigidity, improve running performance on snow, and improve riding comfort. Further, by providing the auxiliary siping, the rigidity between the center block and the other blocks is made uniform, and the riding comfort is improved.
In addition, by dividing each block into small blocks by the main siping provided on land parts other than the center land part, the rigidity of the blocks is reduced, so that running performance on snow is improved and riding comfort is improved. By providing the auxiliary siping, it is possible to further reduce the rigidity of each block, further improve running performance on snow, and improve riding comfort. Further, the provision of the auxiliary siping greatly increases the running performance on snow and the riding comfort by the tread pattern, widens the selection range of the material of the tread rubber, and reduces the deterioration of other performances.

[Brief description of the drawings]

FIG. 1 is a tread pattern developed view showing an embodiment of the present invention.

FIG. 2 is a tread pattern developed view showing a conventional tire.

[Explanation of symbols]

T-tread, TO-tread end 1 Center main groove, 2 center land, 3 middle main groove, 4 center land 5 Shoulder land, 6, 7 lug groove, 8, 9, 10 Main siping 81, 91, 101 Auxiliary siping

Claims (2)

(57) [Claims] 1. A pneumatic radial tire having an annular tread, a pair of sidewalls continuous to both ends of the tread, and a bead at an inner end of the sidewall, at least two circumferentially substantially straight lines provided on the tread. A main groove extending in the shape of a circle, a center land portion extending circumferentially on a tread equator formed between two main grooves extending across the tread equator, and a land other than the center land. only provided part, one end opening to the main groove, the groove width of the other end to divide the land portion open to the other main groove or the tread end portion into a plurality of blocks
Is provided in the center land portion with a lug groove of 1.5 mm or more and less than 5 mm , and both ends are opened in the main grooves on both sides to divide the center land portion into a plurality of center blocks and tread.
Has an angle of more than 20 degrees and less than 70 degrees with respect to the equatorial plane,
Things that rise to the right and things that rise to the left are arranged alternately
A main sipes you Kukaku a center block in a substantially triangular shape, provided on the center block, one end opening to one of both sides of the main groove, and auxiliary sipes which the other end is terminated inside the center block, the center land Each of the side blocks is provided in each of the blocks of the land portion other than the portion, and one end is opened in the main groove and the other end is opened in the main groove, lug groove or tread end.
It is characterized by comprising a main siping which is divided into small blocks, and an auxiliary siping provided in each small block, one end of which is opened in the main groove or lug groove, and the other end of which is terminated in the small block. Pneumatic radial tire. 2. A block forming a central land portion between four circumferentially extending main grooves provided on a tread, and an equatorial side main groove and a shoulder side main groove, and both ends are provided on both sides. A main siping opening in the main groove of the main land and dividing the block at the central land into two small blocks; and a block forming a shoulder land between the main groove on the shoulder side and the end of the tread; And a main siping opening at the main groove on the shoulder side and opening at the other end at the lug groove or the tread end to divide the block on the shoulder land into two small blocks. The described pneumatic radial tire.